1. Field of the Invention
The present invention relates to a frame structure for a vehicle and a vehicle.
2. Discussion of the Background
There is a conventionally-known vehicle body frame structure for a vehicle, which is intended to reduce the weight of a vehicle and to reduce the manufacturing costs (refer to, for example, Japanese Patent Application Publication No. 2006-103370). The vehicle body frame structure described in Japanese Patent Application Publication No. 2006-103370 has a vehicle body frame including: a front frame portion which supports a front-wheel drive system; a center frame portion which forms a space for occupants; and a rear frame portion which supports a rear-wheel drive system. In the center frame portion, the structure of an underfloor frame is formed to be a two-layer structure having an upper portion and a lower portion. The upper portion includes lower frames and side square-U-shaped frames, and the lower portion includes subframes and upper side frames.
In the vehicle body frame structure described in Japanese Patent Application Publication No. 2006-103370, the structure of the underfloor frame in the center frame portion is formed to be the two-layer structure having the upper and lower portions. This structure sufficiently secures the rigidity of the underfloor frame, but increases the height of the floor, thus leading to an increase in the height of the seats for the occupants. On the other hand, in order to enhance the traveling performance required for vehicles such as MUVs (multi utility vehicle), it is desirable that the vehicles have a low floor and a low center of gravity in addition to an improvement in rigidity of the vehicle body frame.